Nariman-Edit- 3D modelling for everything else you see. 
BisonSales- 3D modelling for a few things in NJ.


NYPD Police computer: 
https://www.gtagaming.com/nypd-police-computer-mod-f3072.html
Great NYPD stations pack 1.0 by AlexVonShep (modified): https://www.lcpdfr.com/downloads/gta4mods/misc/6882-great-nypd-stations-pack/
Ultimate NYPD & NY uniforms mod v2.0 by gorgonut (modified):
https://libertycity.net/files/gta-4/40408-ultimate-nypd-ny-uniforms-mod-v.2.0.html
NYPD and Dept. of Homeland Security Skins Pack by gorgonut (modified): 
https://www.gtainside.com/en/gta4/cars/28669-nypd-and-dept-of-homeland-security-skins-pack/
New York Port Authority Booths! by n8gamez1 (Modified):
https://www.gtagarage.com/mods/show.php?id=9672
Textures for Niko clothes, Ped clothes and Annihilator by GysCO:
https://www.gtagaming.com/textures-for-niko-clothes-ped-clothes-and-annihilator-f32395.html
Trashmaster Real New York by Markus:
https://www.gtaall.com/gta-4/cars/101665-trashmaster-real-new-york.html
Enforcer New York City by NicoandLuis:
https://www.gtaall.com/gta-4/cars/101890-enforcer-new-york-city.html
Police Stockade New York by NicoandLuis:
https://www.gtaall.com/gta-4/cars/101887-police-stockade-new-york.html
MTA R32 Subway by SkylineGTRFreak (modified):
https://www.gtainside.com/en/gta4/trains/47558-mta-r32-subway/
Predator NYPD by Ariel:
https://www.gtaall.com/gta-4/boats/103829-predator-nypd.html
NYPD Police Maverick by Ariel:
https://www.gtaall.com/gta-4/helicopters/103828-nypd-police-maverick.html
Real Shops v2 HD by DevilGTAIV (modified):
https://www.gtagaming.com/real-shops-v2-hd-f24342.html
Viva New-York Mod by Emble (modified):
https://libertycity.net/files/gta-4/29201-viva-new-york-mod.html
Nightclub Retexture - TBoGT style by 6135:
https://www.gtainside.com/en/gta4/mods/138265-nightclub-retexture-tbogt-style/
1988 New Jersey (Alderney) by LoadGamePL (modified):
https://www.gtainside.com/en/gta4/mods/106878-1988-new-jersey-alderney/
1998 Bronx by LoadGamePL (modified): 
https://www.gtainside.com/en/gta4/maps/106177-1988-bronx/
Hard Rock Cafe v2 by MaxiKing30:
https://www.gtainside.com/en/gta4/mods/29864-hard-rock-cafe-v2/
Time Square Hard Rock Cafe by MaxiKing30:
https://www.gtainside.com/en/gta4/mods/33314-time-square-hard-rock-cafe/
Central Park Gate by LexLuthor2109:
https://www.gtagaming.com/central-park-gate-f6200.html
Grand Central Station by LexLuthor2109:
https://www.gtagaming.com/grand-central-station-f6183.html
HD Textures | Airport by DayL:
https://www.gtainside.com/gta4/mods/126836-hd-textures-airport/
HD Textures | Outlook Park by DayL:
https://www.gtainside.com/en/gta4/mods/126837-hd-textures-outlook-park/
HD Textures | Middle Park by DayL:
https://www.gtainside.com/en/gta4/mods/131267-hd-textures-middle-park/
HD Textures | Liberty Island by DayL:
https://www.gtainside.com/gta4/mods/130589-hd-textures-liberty-island/
NYC Statue of Liberty v2.0 by Nobeus:
https://www.gtagaming.com/nyc-statue-of-liberty-v2-0-f30569.html
Real NYC Roadsigns by zyonig:
https://www.gtagarage.com/mods/show.php?id=16343
IV Real Subways by zyonig (modified): 
https://www.gtagarage.com/mods/show.php?id=18092
Vegetation Textures Variety Pack by BisonSales:
https://libertycity.net/files/gta-4/88947-vegetation-textures-by-bisonsales.html
HD Roads Final by DKT70:
https://libertycity.net/files/gta-4/35472-hd-roads-by-dkt70-final.html 
V HQ Vehicle interiors for IV by jacell (modified):
https://www.gtainside.com/en/gta4/cars/134316-v-hq-vehicle-interiors-for-iv/
First Person Mod by (?): 
https://www.moddb.com/games/grand-theft-auto-iv/addons/first-person-mod-v11
TrafficLoad by ikt:
https://www.gtainside.com/en/gta4/mods/37248-trafficload/
REL.Budgeted by NTAuthority:
https://gtaforums.com/topic/744584-reliv-rilbudgeted-population-budget-adjustertaxi-bug-fix/
Fixes and Improvements Pack v3 by Zolika1351:
https://gtaforums.com/topic/909155-iv-fixes-improvements/
Plane Flight Path Improvements by (?):
https://www.gtagaming.com/plane-flight-path-improvements-f33591.html
HQ Radio Icons 1.2 by Sborges98:
https://www.gtainside.com/en/gta4/mods/107596-hq-radio-icons-1-2/
Improved Animations Pack by BDawg:
https://gtaforums.com/topic/958625-improved-animations-pack/
Higher Resolution Miscellaneous Pack for GTA IV by Ash_735 (modified):
https://gtaforums.com/topic/887527-ash_735s-workshop/page/6/#comment-1072246033

NOTICE:
I CANNOT FIND THE OG AUTHOR OF THE RADIO DOWNGRADER, PLEASE REACH OUT AND TELL ME THE AUTHOR SO I CAN CREDIT THEM!!